Modelling crack-tip behaviour in a directionally solidified nickel alloy under fatigue-oxidation conditions

Directionally solidified superalloy, which has elongated large grains, is used for a gas-turbine blade because of its high creep strength. Since the grain size is not small enough in comparison with the size of component and crack, the inhomogeneous microstructure strongly affects the crack propagation behavior. The aim of this research is to clarify the microstructural effect in the creep-fatigue under a transverse load. The experiment reveals characteristic crack path and fluctuation of crack propagation rate in detail. Several intergranular sub-cracks initiated ahead of the tip of main crack occasionally connect with each other and form a complicated crack path. The deformation near the crack tip during a loading cycle is highly dependent on the local grain boundary network, grain shape, and crack shape. The magnitude of da/dN is correlated fairly well with that of local deformation in the vicinity of crack tip. This suggests that the stress field near the crack tip governs the crack propagation.

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heat treatment effect on the structure formation of directionally solidified nickel alloy after slm

10.37904/metal.2021.4235 ◽

2021 ◽

Author(s):

Evgenii BORISOV ◽

Kirill STARIKOV ◽

Artem KIM ◽

Vera POPOVICH ◽

Anatoly POPOVICH

Keyword(s):

Heat Treatment ◽

Nickel Alloy ◽

Structure Formation ◽

Treatment Effect ◽

Directionally Solidified

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Effect of grain boundary fraction on castability of a directionally solidified nickel alloy

Scripta Materialia ◽

10.1016/j.scriptamat.2006.02.032 ◽

2006 ◽

Vol 54 (12) ◽

pp. 2169-2174 ◽

Cited By ~ 21

Author(s):

Y.Z. Zhou ◽

A. Volek

Keyword(s):

Grain Boundary ◽

Nickel Alloy ◽

Directionally Solidified

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Electron Microscopy of Metal-Matrix Composites

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100069016 ◽

1970 ◽

Vol 28 ◽

pp. 404-405

Author(s):

A. Lawley ◽

M. R. Pinnel ◽

A. Pattnaik

Keyword(s):

Electron Microscopy ◽

Metal Matrix Composites ◽

Metal Matrix ◽

Critical Evaluation ◽

Elastic Behavior ◽

Matrix Composites ◽

Directionally Solidified ◽

Fracture Characteristics ◽

Broad Program

As part of a broad program on composite materials, the role of the interface on the micromechanics of deformation of metal-matrix composites is being studied. The approach is to correlate elastic behavior, micro and macroyielding, flow, and fracture behavior with associated structural detail (dislocation substructure, fracture characteristics) and stress-state. This provides an understanding of the mode of deformation from an atomistic viewpoint; a critical evaluation can then be made of existing models of composite behavior based on continuum mechanics. This paper covers the electron microscopy (transmission, fractography, scanning microscopy) of two distinct forms of composite material: conventional fiber-reinforced (aluminum-stainless steel) and directionally solidified eutectic alloys (aluminum-copper). In the former, the interface is in the form of a compound and/or solid solution whereas in directionally solidified alloys, the interface consists of a precise crystallographic boundary between the two constituents of the eutectic.

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Determination of interface width using EELS fine structure changes

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100087963 ◽

1991 ◽

Vol 49 ◽

pp. 730-731

Author(s):

Vinayak P. Dravid ◽

M.R. Notis ◽

C.E. Lyman

Keyword(s):

Fine Structure ◽

Materials Science ◽

Input Parameter ◽

Core Loss ◽

Directionally Solidified ◽

Interface Width ◽

Structure Changes ◽

Important Input ◽

Directionally Solidified Eutectics

The concept of interfacial width is often invoked in many materials science phenomena which relate to the structure and properties of internal interfaces. The numerical value of interface width is an important input parameter in diffusion equations, sintering theories as well as in many electronic devices/processes. Most often, however, this value is guessed rather than determined or even estimated. In this paper we present a method of determining the effective structural and electronic- structural width of interphase interfaces using low- and core loss fine structure effects in EELS spectra.The specimens used in the study were directionally solidified eutectics (DSEs) in the system; NiO-ZrO2(CaO), NiO-Y2O3 and MnO-ZrO2(ss). EELS experiments were carried out using a VG HB-501 FE STEM and a Hitachi HF-2000 FE TEM.

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A TEM investigation of a hyper-eutectic lead-tin alloy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010010487x ◽

1988 ◽

Vol 46 ◽

pp. 562-563

Author(s):

John A. Sutliff

Keyword(s):

Volume Diffusion ◽

Eutectic Mixture ◽

Precipitation Reaction ◽

Directionally Solidified ◽

X Ray Diffraction ◽

X Ray ◽

Transmission Electron ◽

Diffusion Controlled ◽

Discontinuous Precipitation Reaction ◽

Controlled Precipitation

Near-eutectic Pb-Sn alloys are important solders used by the electronics industry. In these solders, the eutectic mixture, which solidifies last, is the important microstructural consituent. The orientation relation (OR) between the eutectic phases has previously been determined for directionally solidified (DS) eutectic alloys using x-ray diffraction or electron chanelling techniques. In the present investigation the microstructure of a conventionally cast, hyper-eutectic Pb-Sn alloy was examined by transmission electron microscopy (TEM) and the OR between the eutectic phases was determined by electron diffraction. Precipitates of Sn in Pb were also observed and the OR determined. The same OR was found in both the eutectic and precipitation reacted materials. While the precipitation of Sn in Pb was previously shown to occur by a discontinuous precipitation reaction,3 the present work confirms a recent finding that volume diffusion controlled precipitation can also occur.Samples that are representative of the solder's cast microstructure are difficult to prepare for TEM because the alloy is multiphase and the phases are soft.

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The effect of back-melting on the continuity of crystallographic orientation and composition in HgZnTe

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100133114 ◽

1992 ◽

Vol 50 (2) ◽

pp. 1696-1697

Author(s):

H.J. Zuo ◽

M.W. Price ◽

R.D. Griffin ◽

R.A. Andrews ◽

G.M. Janowski

Keyword(s):

Directional Solidification ◽

Space Shuttle ◽

Solidification Process ◽

Space Experiment ◽

Infrared Detection ◽

Directionally Solidified ◽

Crystallographic Defects ◽

Semiconducting Alloys ◽

Uniform Composition ◽

Growth Experiments

The II-VI semiconducting alloys, such as mercury zinc telluride (MZT), have become the materials of choice for numerous infrared detection applications. However, compositional inhomogeneities and crystallographic imperfections adversly affect the performance of MZT infrared detectors. One source of imperfections in MZT is gravity-induced convection during directional solidification. Crystal growth experiments conducted in space should minimize gravity-induced convection and thereby the density of related crystallographic defects. The limited amount of time available during Space Shuttle experiments and the need for a sample of uniform composition requires the elimination of the initial composition transient which occurs in directionally solidified alloys. One method of eluding this initial transient involves directionally solidifying a portion of the sample and then quenching the remainder prior to the space experiment. During the space experiment, the MZT sample is back-melted to exactly the point at which directional solidification was stopped on earth. The directional solidification process then continues.

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